🎯 Objectives
The students would be familiarized with the role of higher order brain functioning 🧠⚡. This is the role of the highly evolved areas of the brain 📈, the cerebral cortex 🧠.
📋 Brain Correlates
- Language 🗣️ Speech Production 💬 Comprehensions 👂, Aphasias 🚫🗣️
- Visuospatial 👁️📐, the man who mistook his wife for a hat? 🎩❓
- Apraxia's 🚫🤚 (Neuropsychological tools 🔧)
- Brain correlates of Learning and Memory 🧠💾, Amnesia 🚫💭, Verbal/Nonverbal memory 📚
- (Neuropsychological tools 🔧🧪)
🧠 Higher Order Functioning
When we refer to the higher order functioning ⚡🧠, we are focusing on the cortical control of major functions 🎛️. As we stated in our earlier chapters 📚, the higher the animal on the evolutionary scale 📈 the more the cerebral cortical control over these functions and development of newer functional connections 🔄.
🔬 Behavioral Neurosciences Goals
Behavioral neurosciences is attempting to 🎯:
- Understand functions such as language 🗣️, emotions 😊😢, learning 📖, memory 💭 and psychopathology 🧠⚠️
- Develop models to explain the function of cortical areas as they relate to behavior 🧠↔️🎭
We would discuss language 🗣️ which humans have evolved as specialized communication 👥. This is not just communication but language is intertwined with development of healthy and pathological behaviors 🧠✅❌.
🗣️ Language
Language: This is among the most important higher order function 🧠⚡, and is uniquely human 👨 but not so, because if we look around us we can see examples of communication in other animals as well 🐾. For example, Bird songs 🦅🎵 dog's growling 🐕 are complex communication system 🗣️, with the variation - which can communicate the state of one dog to another 🐕↔️🐕 – even across species communication can take place through these signals 🌍.
🐒 Limbic vs Cortical Control
In the squirrel monkey's 🐒 language comes under limbic control 🧠, in human's 👨 vocalization is both:
- Limbic (nonverbal) 😭: cries, groan, gasps 😮
- Cortical (verbal, and symbolic) 🗣️💬: structured language
The development of language is based on capabilities already present in the nervous system 🧬🧠.
🧬 Evolution of Language
Therefore, the evolution of language involves 📈:
• Appropriate development and evolution of cognitive and communication abilities and apparatus 🧠🗣️. The abilities of primates are limited with categorization of calls 🐒 i.e., the alarm calls are different from the mating calls 🔔❤️. These do not have the sophisticated mechanism for variation as humans have 👨⚡.
• A structure of language in a formal system of signs and symbols 📝🔤
• Development of the language in children 👶 who have the capability of doing so 🧠✅
🦴 Physical Apparatus for Speech
Speech is difficult (fairly impossible) for a non-human primate 🐒❌ and young humans 👶 as the appropriate mechanisms have not developed physically 🦴. It is only about 50,000 years ago ⏰ the tracts and physical apparatus for language evolved 📈 (this is controversial 🤔 and the brain 🧠 and language capabilities 🗣️ must have evolved together 🔄).
🐵 Language in Non-Human Primates
Communication Non human primates: primitive 🐒, gestures 🤚, postures 🧍, (more nonverbal 🚫💬) calls of different types: alarm 🚨, distress 😰, territoriality 🏠 threat 😡 but not complex communication such as, "how are you today?" 👋 This is not possible for animals even the higher order primates 🐵 (except for humans 👨).
🐵 Washoe the Chimpanzee
In innovative experiment carried out by Gardiner and Gardiner 👨🔬👩🔬 where they trained a chimpanzee Washoe 🐵 to communicate with humans using the American Sign Language 🤟. The chimpanzee learnt over a hundred signs 💯 and exhibited capability of communication equivalent to two years (human) 👶 with "slot grammar" such as a human child would use: long darkness for tunnel 🚇. However this chimpanzee was not able to verbalize 🚫🗣️.
🔊 Primate vs Human Language
In primate's one call, one sound is communicating one message 🐒🔊, whereas human language uses a combination of a few sounds to lead to thousands of words 🗣️💬 (with intonations entirely different interpretation 🎵, grammatical limitations and boundaries 📝. The same sound uttered in different ways in different situation leads to a different interpretation 🔄).
🧬 Shared Genetics
However, many experimenters such as Premack and Premack 👨🔬 have led us to rethink 🤔. First and foremost, man and chimpanzee share 96% genes 🧬 it is possible that chimpanzee can develop language as humans did 🐵➡️👨.
🐵 Lana at Yerkes Primate Institute
Lana 🐵, a chimpanzee at the Yerkes Primate Institute 🏢, developed grammatical relationships on her own 📝 such as saying "Lana wants banana" 🍌 and connected novel strings of symbols using computer 💻 and other symbols 🔣, innovation in picking up and expanding on the learnt words 💡 demonstrated that there were capabilities in the primates closest to humans 🐵≈👨. There was not much learning by interaction and socialization 🚫👥.
👶 Language Development Requires Interaction
We must understand that language development requires learning by interaction and socialization 👥🗣️. How does a child learn a language? 👶❓ Through imitation 🔄 and reinforcement ✅ of the words expressed till they become meaningful and can get the desired objects such as candy 🍬 or food 🍽️.
Even human children if brought up without such stimulation do not develop language 🚫🗣️ even though they have the capability of doing so 🧠✅. For example, children reared by wolves 🐺 don't have the human language 🚫💬; they can only communicate like the wolves by snarling 😤, growling 😡 or barking 🐕.
💬 Speech Production and Comprehension
In order to understand speech 🗣️, we move through the absence of speech 🚫. Stroke 🏥, accident 🚗 or any other traumas ⚠️ which lead to loss of speech 🚫🗣️.
🚫 Aphasia
Aphasia: One of the disorders of speech is Aphasia which is disorder of comprehension 👂❌ or production 💬❌ of speech.
Speech production: is based on several abilities 🎯:
- Sensation and perception of the surrounding 👁️👂
- Memories and imagination 💭
- Connection between past and present ⏰🔄
- Vocal capabilities 🗣️
- Articulation musculature 👄💪
🏥 Paul Broca's Discovery
Paul Broca 👨⚕️ a French neurologist described a patient who had great difficulty in producing speech 🚫💬. Broca described the cases of 14 patients at a conference 📋 – and his paper went unnoticed ⚠️. These were stroke patients 🏥 who had middle cerebral arterial supply of blood to the Sylvain fissure affected 🩸 leading to similar difficulties. He then identified this area as inferior prefrontal cortex 🧠.
🗣️ Broca's Aphasia
Broca's Aphasia (Aphasia: Greek word 🇬🇷, A: without 🚫, phasia: speaking out 🗣️):
Broca's area in the frontal lobe 🧠 controls the musculature 💪 and other mechanisms (air vibrating in the vocal cords 🗣️) and damage to inferior left frontal lobe ⚠️, The Broca's area contains motor memories of tongue, lips, jaw, coordinated and sequenced movements 👅👄. It lies adjacent to the controls of face and lip 😮, though the posterior parts of Cerebral Cortex want to say it 💭 but the frontal damaged area makes it difficult 🚫💬.
📊 Characteristics of Broca's Aphasia
Broca's Aphasia: is mainly a disorder of expressive speech 💬❌. This results in slow laborious and non-fluent speech 🐌🗣️. Broca's aphasics make an effort to locate words to express what they want to say 🤔, they mispronounce words but usually come out with meaningful sentences 📝✅.
These aphasics have difficulty in small grammatical mistakes such as the use of a, the, some, in, about (linking words 🔗❌).
They can articulate little words with grammatical meanings: Function words are difficult ❌, but content words come easily ✅, as they can convey what the patient is trying to say 💭:
"Ah Monday, Ah DAD, Paul and Dad, hospital… Wed…. 9p.m." 💬 (Good glass 1976, p 278 cf Carlson 1994 and Bridgeman 1988 📚)
Their speech is telegraphic 📟, and there is no impairment of speech comprehension 👂✅.
🔬 Neuropsychological Tests for Broca's Aphasia
A series of Neuropsychological tests which can assess Broca's aphasia are for example 📋:
A picture is shown to the patient where a horse 🐴 and a cow 🐄 are standing in the same posture. In one picture the cow is kicking the hind leg of the horse with its hind legs 🦵, and the second picture the kicking is reversed 🔄. There are questions of what is happening who is kicking who and where? ❓ The correct grammatical order is required 📝 (Shwartz, Saffron and Marin 1980 👨🔬).
Task sequencing commands are also given 📋, word order is disrupted because they difficulty in carrying out a sequenced response 🔄❌. If this area is stimulated it leads to a coordinated movement ⚡💪, lesioning blocks the coordinated sequence 🚫. Questions can be "Pick up a red ball and touch green circle" 🔴⚪, difficulty in saying it is difficulty of muscles of speech production 💪🗣️❌.
👂 Speech Comprehension
In Speech Comprehension 👂 the areas in the auditory lobe 🧠 are involved. Wernicke's area is located in the Middle and Posterior region of Superior Temporal Gyrus 🧠.
The speech comprehension area collects information 📡, matches 🔄, recognizes ✅, and analyzes it 🧠 and sends it to the articulation areas (through the arcuate fasciculus 🧠🔗).
🔊 Recognition of a Word
Recognition of a word involves 🗣️:
- a) Sensation 👂
- b) Perception 🧠
- c) Memories of the sequencing of sound articulation 💭🔊
Damage to this region leads to receptive speech disorder 👂❌.
🗣️ Wernicke's Aphasia
Primary characteristic of Wernicke's aphasia is that the speech appears better than Broca's ✅ fluency rhythm as the articulation intact 🗣️ but what they say does not make sense ❌💬. However, they cannot recognize the deficit 🚫🤔. Poor speech comprehension 👂❌ and production of string of meaningless words 🗣️❓ characterizes Wernicke's aphasia.
Wernicke's patients are not aware of their problems with speech 🚫💭. Wernicke's patients not aware of their problems are speech 🤷. They are not aware that people don't understand them 🚫👥, or they are having any difficulty 🤔❌. What they say or hear is incomprehensible to them and others 💬❓.
💬 Example of Wernicke's Speech
Speech appears correct to a foreigner 🌍 but to those who know the language it is nonsensical 💬❌. As an example 📋:
When Asked What Do You Do? 🤔
The patient replies 💬, "Mista oxycge,wann tell happened when happened, herent, kell, cam ho, renrapiers" ❓ and the patient is satisfied that he was answering the question ✅😊.
🔬 Neuropsychological Tests for Wernicke's Aphasia
The neuropsychological tests for speech comprehension 📋 e.g. the Patient tested through questions of receptive speech 👂: point to pen ✏️, your nose 👃
The deficit is at the semantic level 💭 (meaning of the words 📝) their deficit is in understanding speech and its meaning 👂💬❌.
📚 References
- Carlson, N. R. (2005). Foundations of physiological psychology. Pearson Education New Zealand.
- Pinel, J. P. (2003). Biopsychology. (5th ed). Allyn & Bacon Singapore.
- Bloom, F., Nelson., & Lazerson. (2001), Behavioral Neuroscience: Brain, Mind and Behaviors. (3rd ed). Worth Publishers New York
- Bridgeman, B. (1988). The Biology of Behavior and Mind. John Wiley & Sons, New York
- Brown, T.S. & Wallace, P.S. (1980). Physiological Psychology. Academic Press, New York
- Bradshaw, J. L. & Mattingley, J. B. (1995). Clinical Neuropsychology: Behavioral and Brain Sciences. ACADEMIC PRESS